<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">

    <h2 class="title" :class="[active,line]">{{message}}</h2>
    <h2 class="title" :class="getclasses()">{{message}}</h2>

  </div>
  <script src="../js/vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        message: '你好啊',
        active: 'aaaaaa',
        line: 'bbbbbbb'
      },
      methods: {
        getclasses: function () {
          return [this.active, this.line]
        }
      },
    })
  </script>
</body>

</html>